Information converter

ABSTRACT

An information converter for converting analog-information not only into a digital value but also into a fractional analog value between digital values. An input capacitor stores an analoginformation charge. An input is electrically connected with this input capacitor for charging the latter to an extent determined by the analog information. An output capacitor is provided with a capacitance less than that of the input capacitor. An oscillating circuit is electrically connected with both of the capacitors for carrying out a number of charge-discharge cycles during which the output capacitor is charged from the analog-information charge of the input capacitor up to a predetermined digital-value charge, then discharged, then charged again, and so on, until, in the event that the analog-information charge is not a precise multiple of the digital-value charge, both of the capacitors assume a balanced condition where they respectively have equal residual analog charges each of which is less than the digitalvalue charge. A detecting circuit is electrically connected with at least one of the capacitors for detecting the residual analog charge.

United States Patent Nobusawa INFORMATION CONVERTER PrimaryExaminerSamuel S. Matthews Assistant ExaminerMichael L. Gellner 75 I t zT k N b T k J men or su usawa 0 apan Attorneyl-larold D. Stemberg et al.[73] Assignee: Asahi Kogaku Kogyo Kabushiki Kaisha, Tokyo-to, JapanABSTRACT [22] Filed: Apr. 10, 1972 An information converter forconverting analogl l PP N03 242,668 information not only into a digitalvalue but also into a fractional analog value between digital values. An[30] Foreign Application Priority Data input capacitor stores ananalog-information charge. A 20 19.71 Ja an 46/249312 An input iselectrically connected with this input ca- 1971 J p 46 32449 pacitor forcharging the latter to an extent determined 197 Japan 46/34983 by theanalog information. An output capacitor is pro- 1971 Japan 46/2493]vided with a capacitance less than that of the input caapan pacitor. Anoscillating circuit is electrically connected with both of thecapacitors for carrying out a number of charge discharge cycles duringwhich the output [58] d CE pacitor is charged from theanalog-information charge 1e 0 can 340/347 of the input capacitor up toa predetermined digitalvalue charge, then discharged, then chargedagain, and so on, until, in the event that the analog- [56] ReferencesCited information charge is not a precise multiple of the UNITED STATESPATENTS digital-value charge, both of the capacitors assume a 3,251,0525/1966 Hoffman et al 340/347 balanced condition where they respectivelyhave equal 3,603,799 9/ 1971 Nobusafva i 250/214 residual analog chargeseach of which is less than the 3'633473 1/1972 Yashuhmm 95/10digital-value charge. A detecting circuit is electrically 3,651,7443/1972 Okada 95/10 connected with at least one of the capacitors fortecting the residual analog charge.

Claims, 10 Drawing Figures o 0 c /4 21/? l 7 l 5' J 3 9 J 5* f N 7 T 2 T22 PATENTED UB1 16 m3 SHEET 2 BF 5 Illl 31 PFJENTED UN 15 i975 SHEET 5[IF 5 INFORMATION CONVERTER BACKGROUND OF THE INVENTION The presentinvention relates to information converters.

Thus, the present invention relates to that type of informationconverter which is capable of presenting information in the form of anelectrical quantity, for example, and which can then operate on thiselectrical quantity so as to bring about automatic controls. Thus, thepresent invention may be used in connection with light at an object tobe photographed, this light being detected so as to form analoginformation which can be presented in the form of an electricalquantity, and then this latter quantity can be operated upon to controla light meter, for example, giving to the operator an indication of thelight value, or this quantity may be operated upon to bring aboutautomatic controls of the shutter of a camera, for example. It is to beunderstood, however, that these are only examples of the manner in whichthe invention can be put to practical use and that other practical usesare equally available for the present invention.

In the case of cameras, it is well known to provide automatic shuttercontrols capable of automatically determining the exposure time andautomatically operating the shutter accordingly. Conventional controlsof this type utilize, for example, an internal light-receiving systemwhich receives light which has already travelled through the objectiveof the camera. In the past few years it has become customary in certaintypes of cameras to select, in accordance with the light received by theinternal system, a given timing resistor so that the exposure time willbe controlled according to that one of a number of timing resistorswhich is automatically selected. However, this type of control hasinherent disadvantages. The selection of one of a series of timingresistors necessitates a stepped adjustment of the exposure time. Thus,such structures can only provide exposure times which have predeterminedincrements from one to the next, and it is not possible to achieve acontinuous adjustment of exposure time. Since it seldom happens that thelight at the oject to be photographed and the other factors such as filmspeed and diaphragm aperture will be precisely represented by a giventiming resistor, there is an inherent inaccuracy in this type ofstructure, and highly precise exposure times cannot be achieved becauseof the stepped type of selection which is necessitated by this type ofstructure.

Thus, with conventional structure of the above type, and thesestructures include not only light meters and cameras, but also othertypes of devices such as communication apparatus, for example, thelimitation of the controls to stepped or incremental values represents aserious disadvantage since values between the incremental values must beneglected.

SUMMARY OF THE INVENTION It is therefore a primary object of the presentinvention to provide an information converter which will avoid the abovedrawbacks.

Thus, it is an object of the present invention to provide an informationconverter which can operate effectively to provide a control not onlyaccording to stepped values but also according to values between thestepped values so as to achieve a truly continuous control.

A further object of the present invention is to provide a structurewhich can achieve these results by making use of relatively simplecircuitry and components which operate 'very reliably.

In addition it is an object of the present invention to provide thepossibility of achieving the desired results simply by adding toconventional structure a structure which will give values between theincremental values which can be obtained in a conventional manner.

The objects of the present invention also include the provision of astructure which will operate in a fully automatic manner to achieve theabove results, without requiring any special manipulations by theoperator, so that as far as an operator is concerned although a devicemay include the structure of the invention, it is not necessary for theoperator to learn new procedures.

Thus, the present invention relates to an information converter of thetype where analog information, such as analog information determinedelectrically from light received from an object which is to be photographed, is converted into a series of digital quantities of equalpredetermined magnitudes, with the converter also providing anadditional residual analog quantity which is less than a digitalquantity.

Therefore, the primary purpose of the invention is to convertelectrically converted information such as information according tolight received from an object to be photographed or any other convenientanalog information into a series of additional quantities and a residualanalog quantity which may be regarded as a remaining fractional valuefor use in the control of a camera shutter, an exposure meter, or anyother apparatus or instrument.

According to the invention the information converter includes an inputcapacitor means for storing an analog-information charge. An input meansis electrically connected with the input capacitor means for chargingthe latter to an extent determined by the analog information. An outputcapacitor means has a capacitance less than the input capacitor means.An oscillating circuit means is electrically connected with both of thecapacitor means for carrying out a number of chargedischarge cyclesduring which the output capacitor means is charged from theanalog-information charge stored by the input capacitor means up to apredetermined digital-value charge, then discharged, then again chargedfrom the input capacitor means up to the digital-value charge, and soon, until, in the event that the analog-information charge is not aprecise multiple of the digital-value charge, both of the capacitormeans assume a balanced condition where they respectively have equalresidual analog charges each of which is less than the digital-valuecharge. A detecting means is electrically connected with at least one ofthe capacitor means for detecting this residual analog charge.

By incorporating the structure of the invention into a timing resistorselecting type of electric shutter control, with the analog-informationbeing provided by photoelectrically converting light from the object tobe photographed into the form of a charge stored by an input capacitormeans, it is possible to discharge the latter during a number of cyclesby a suitable oscillating circuit means through an output capacitormeans which can be repeatedly charged up to a predetermineddigital-value charge corresponding to light equal to l L.V. (lightvalue). It is possible to achieve a continuous adjustment of exposuretime with the residual analog charge being less than 1 L.V. Thus whenthe actual intensity of light corresponds to a value between twoadjacent exposure time graduations which are graduated in accordancewith given multiples, the trigger voltage of the electric shuttercontrol circuit can also be controlled with the information converter ofthe invention in accordance with the residual analog charge whichremains when both of the capacitor means are in their balancedcondition, so that a continuous adjustment of exposure time can beachieved. However, because of the characteristics which are associatedwith charging and discharging operations of a pair of capacitors whichare included in the information converter of the invention, a certainbias resistor will be required in the trigger circuit of the electricshutter controls.

Although the invention is described above in connection with shuttercontrols of a camera, it is equally possible to incorporate theinvention into an electric exposure meter by the use of suitablecircuits. In this case if the photoelectrically converted informationfrom the light of the object to be photographed is used as the inputanalog information, there will appear across the terminals of the outputcapacitor means a series of digital charges and a final residual analogcharge with the total of the digital-value charges plus the residualanalog charge corresponding precisely to the intensity of the lightwhich is to be measured. Thus such a meter may be provided with anindicator means which will indicate each L.V. in a stepped manner,corresponding to the number of digital-value charges or in other wordsto the number of cycles that the output capacitor means is charged anddischarged, while a second indicator may be incorporated .into the lightmeter to provide a fractional indication of a light value betweenadjacent whole light values, so that in this way such a meter canprovide a continuous indication of accurate exposure time.

As is apparent from the above, in the description which follows theexpression digital information signifies the terminal voltage up towhich the output capacitor means is charged just before the moment whenit is discharged, this terminal voltage being a predetermined constantvoltage level. The residual analog charge signifies the terminal voltageat either of the capacitors at the time when these terminal voltagesbecome equal to each other and have a value less than the digital-valuecharge.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way ofexample in the accompanying drawings which form part of this applicationand in which:

FIG. 1 is a wiring diagram of one embodiment of the invention;

FIG. 2 is a wave diagram illustrating output pulses provided with theinformation converter of FIG. 1;

FIG. 3 schematically illustrates the invention as applied to a lightmeter;

FIGS. 46 respectively illustrate three different embodiments of theinvention each of which utilizes a Schmitt circuit;

FIGS. 7 and 8 respectively illustrate embodiments of the inventionutilizing monostable multivibrators;

FIG. 9 illustrates an embodiment of the invention where a simple switcharrangement forms an oscillating circuit; and

FIG. 10 illustrates a further embodiment of the invention whereautomatic controls are provided for the switch arrangement of the typeshown in FIG. 9.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIG. 1, theinformation converter of the invention which is illustrated therein isshown as applied to a camera for controlling a shutter which has atiming resistor selection type of control system. The illustratedinformation converter includes an input capacitor means 6 for storing ananalog-information charge. This input capacitor means 6 is electricallyconnected with an input means which charges the capacitor means 6 to anextent determined by the analog information. The input means includes aphotosensitive light-receiving element 1 which receives light from theobject which is to be photographed. This photosensitive means 1 convertsthe received light into a corresponding electrical quantity. Thelight-receiving element 1 is electrically connected in series with alogarithmic conversion diode 2. The circuit includes a power source 4,formed by one or more batteries, for example, and this power source 4 isconnected in series with a transistor 3 of the input means. Thelightreceiving element 1 is connected across the base and collectorterminals of transistor 3 while the logarithmic conversion diode isconnected across the base and emitter terminals, so that thesecomponents form an input means in the form of a photographic conversioncircuit of the information converter of the invention.

The emitter circuit of the transistor 3 includes a variable resistor 5,and the input capacitor means 6 is connected in parallel with thevariable resistor 5.

The information converter of the invention includes an output capacitormeans 7 which has a capacitance less than that of the input capacitormeans 6. The capacitor means 6 and the capacitor means 7 areelectrically connected to each other through a selecting switch 8 whichis normally in the position shown in FIG. 1 where the switch 8 is closedat its contact a, thus maintaining the capacitor means 6 electricallyconnected with the variable resistor 5 and the other components 1-3 ofthe input means. The switch 8 has a normally open contact b. Thus,during normal operation the analog information in the form of the lightat the object to be photographed is stored by the input capacitor means6 in the form of an analog-information charge. Just prior to exposure offilm, in response to depression of a shutter-tripping plunger of thecamera, the switch 8 will be operated so as to become open at itscontact a and closed at its contact b, this operation of the switch 8taking place in a well known manner. Therefore, after theanalog-information has been stored in the form of a charge at the inputcapacitor means 6, the switch 8 is actuated to disconnect the capacitormeans 6 from the input means and instead connect it electrically to theoutput capacitor means 7. As a result, when the switch 8 is closed atits contact b the capacitor means 6' discharges in order to charge thecapacitor means 7 which is inserted into the discharge circuit ofcapacitor means 6 by the above operation of the switch 8. This dischargecircuit for the input capacitor means 6 includes a variable resistor 9which is capable of adjusting the charging time of the output capacitormeans 7. Also the discharge circuit includes a switching transistor 10which operates to temporarily open the discharge circuit of the inputcapacitor means 6, this opening of the discharge circuit by thetransistor taking place simultaneously with discharge of the outputcapacitor means 7 after the latter has been charged up to apredetermined potential corresponding to a digital-value charge. Thus,the transistor 10 forms part of an oscillating circuit means whichenables the output capacitor means 7 to be charged up to a predetermineddigital-value charge, then discharged, and then when the disconnectionof capacitor 6 from capacitor 7 is terminated by the transistor 10 thecapacitor 7 can again be charged up to the predetermined digital valuecharge, so that in this way the oscillating circuit brings aboutrepeated charge-discharge cycles at the output capacitor means 7.

The oscillator circuit means of FIG. 1 also includes a UJT (uni-junctiontransistor) 11 connected at its emitter to the positive terminal of theoutput capacitor means 7 while the UJT 11 is coupled at one of its baseterminals to an output resistor 12 and to the base of a switchingtransistor 13 of the oscillating circuit means. The collector ofswitching transistor 13 and the base of the first switching transistor10 which cyclically opens the discharge circuit of capacitor 6 areelectrically connected to each other so as to form in this way anelectric feedback circuit.

In FIG. 1 the components 14-24 are electrically connected to form acircuit according to which the exposure time is incrementally controlledin steps by automatic selection of a timing resistor. This part of thecircuit includes a light-receiving element 14, a selection circuit 15connected thereto for transmitting a selection signal according to whicha given timing resistor will be selected, a timing resistor-selectingcircuit 16 electrically connected to the selection-signal circuit 15 andincluding a plurality of timing resistors, a timing capacitor l7,transistors 18 and 19 which form a voltagecomparing circuit, anelectromagnet 20 which determines in a known way when the exposure willbe terminated, a switch 21 for starting operation of the shutter, thisswitch operating in response to depression of the shutter-operatingplunger of the camera, a trigger resistor 22 capable of developing atrigger voltage, a bias resistor 23 for biasing the trigger circuit, andthe power source switch 24.

The above structure of FIG. 1 is capable of achieving a continuousexposure-time adjustment. For the purpose of describing the operation,it may be assumed as an example that the condition of the light at theobject to be photographed is such that the light has a light value(L.V.) which is equal to 12.4.

Under these conditions where the shutter controls are not provided withthe information converter of the invention, the circuit 15 willautomatically transmit to the circuit 16 a signal which will select atthe circuit 16 a timing resistor corresponding to L.V. 12.0. Therefore,the exposure time will be determinedby the time constant which in turnis determined by the selected timing resistor and the timing capacitor17. As a result the residual L.V. of 0.4 cannot be used for control ofthe exposure time and will instead be neglected as an inevitable errorinherent with a structure of this type. In contrast, however, with thepresent invention it is capable of picking up this residual L.V. 0.4 asa residual analog charge by utilizing the information converter of theinvention, and this residual analog charge can be used to control thetrigger voltage of the shutter controls.

Thus, referring to FIG. I when the switch 24 is closed both of thelight-receiving elements 1 and 14 will respond to light at the object tobe photographed. At this time the timing resistor selection-signalcircuit 15 produces a timing resistor selection signal in response tothe light at the object to be photographed so as to thereby bring aboutan automatic selection of a timing resistor in the circuit 16, and nowthe switch 21 is closed, for example in response to selection of aresistor at the circuit 16, so that the shutter opens in order to startan exposure. However, in the particular example used for illustrationthe selected timing resistor will correspond only to L.V. 12.0, and notto L.V. 12.4, which is assumed to be the actual precise condition of thelight at the object which is to be photographed. information However,with the invormation converter of the invention simultaneously with thetravel of light to the element 14 the light has also been received bythe element 1, and the information converter of the invention has beenset into operation upon closing of the switch 24, so that the inputmeans formed by components 1, 2, 3, 5 operates to store at the inputcapacitor means 6 an analog-information charge corresponding to thecondition of the light at the object to be photographed. This of coursetakes place at this time through the contact a of the selecting switch8. As has been pointed out above, just prior to opening of the shutterthe selecting switch 8 is automatically displaced to open the circuit atthe contact a and close the circuit at the contact b. Thus, at this timethe input capacitor means 6 and the output capacitor means 7 areelectrically connected to each other by way of the abovedescribedoscillating circuit means of the invention. With this oscillatingcircuit means at the instant when the output capacitor means 7 has beencharged up to the digital-value charge corresponding to 1 L.V., UJT l 1will momentarily respond in order to bring about a complete discharge ofthe output capacitor means 7, with the transistor 10 operating at thistime to disconnect the capacitor means 6 from the capacitor means 7, andimmediately after the complete discharge of the capacitor means 7, theoscillating circuit means responds to again connect the input capacitormeans 6 to theoutput capacitor means 7 so that the latter again chargesup to the digital-value charge, and so on. Thus with the oscillatingcircuit means of the invention a number of charge-discharge cycles arecarried out at the output capacitor means 7 with the latter repeatedlybeing charged up to the predetermined digital-value charge and thendischarged.

The wave-form diagram of FIG. 2 illustrates the oscillating conditionbetween the terminal voltage of the output capacitor means 7 and UJT 11.As is apparent from FIG. 2, the analog-information stored at thecapacitor means 6 will reproduce a series 'of chargedischarge cycles atthe capacitor means 7.

During the above operation of the information converter of the inventionthe charge at the capacitor means 6 will diminish, and finally, in theevent that the analog charge initially stored in the capacitor means 6is not a precise multiple of the digital-value charge to which thecapacitor means 7 is repeatedly charged, there will remain at the inputcapacitormeans 6 as well as the output capacitor means 7 a residualanalog charge which is less than the digital-value charge. In otherwords after repeatedly carrying out the above cycles the capacitors 6and 7 will reach a balanced condition where these capacitors have aresidual analog charge which is a fraction of the digital-value chargeup to which the capacitor means 7 is repeatedly charged before beingdischarged at each cycle. Thus, at this time the discharge of inputcapacitor means 6 will be terminated and the information converter willassume an idle condition. Of course, the charge which is now stored atthe output capacitor means 7 is not discharged but is maintainedcontinuously, and in the example of FIG. 1 the terminal voltage of theoutput capacitor means 7 is now applied directly to the trigger circuitof the electric shutter controls. Thus, the final residual analog chargeretained by the output capacitor means 7 will act across the terminalsof the trigger resistor 22 in the form of a trigger voltage which isbiased by transistor 19 and bias resistor 23.

All of the above operations take place just prior to release of theshutter to make an exposure. The switch 21 will close in order to startthe operation of the shutter, and the shutter will open for apredetermined interval and then close automatically in response tooperation of the electromagnet 20 in a well known manner. This exposuretime is determined by the controlled trigger voltage and the timeconstant, with the latter being determined in accordance with theselected timing resistor and the timing capacitor 17.

Referring now to FIG.3, there is illustrated therein an embodiment ofthe invention where the information converterv forms part of a lightmeter. This embodiment of the invention includes an informationconverter, a pulse counter circuit, and an exposure meter section. Theinformation converter which forms part of the embodiment of FIG.3 isidentical with that included in the camera of FIGJ, so that thecorresponding components are designated by the same referencecharacters. These components operate in P163 in precisely the mannerdescribed above in connection with FIG.1.

The pulse counter circuit of FIG.3 is made up of a plurality ofthyristors 25 which are connected in parallel and bridged across eachpair of adjacent anodes by a capacitor 26 so that through this circuitryeach stage returns a pulse to the the stage. The several gates of thethyristors 25 are respectively connected with diodes 27 in a forwarddirection, while tha anodes are all connected to one of the baseterminals of UJT of the information converter so as to enable thedigital information to be transmitted. Gate resistors 28,actuationregulating resistors 29, and capacitors 30 are also connectedinto the circuit as shown in FIG.3. In addition, the meter includes anindicator means for indicating successive light values, and thisindicator means includes lamps 31 respectively connected into the anodecircuits of the thyristors 25. The circuitry is calibrated in such a waythat the several lamps 31 indicate successive light values with theinterval from one lamp to the next being equal to l L.V.

The circuitry of FIG. 3 includes a transistor 32 which acts to amplifythe residual analog charge remaining at the output capacitor means 7 ofthe information converter after the series of charge-discharge cyclesreferred to above. The emitter of transistor 32 is coupled with avariable resistor 34 for transmitting the residual analog charge to amoving coil 33 of the meter. This moving coil 33 is situated in theexposure meter section in such a way that it assumes an angular positioncorresponding to the magnitude of the residual analog charge, and it isconnected in a known way with a needle which moves along a scalegraduated according to fractions of 1 L.V.

Thus, with this embodiment of the invention the terminal voltage at theoutput capacitor means 7 appearing when it has been charged up to thepredetermined digital value during each operating cycle, or an operatingvoltage of UJT 11 is set to correspond to a value of l L.V. so as tothereby bring about oscillations with an interval corresponding to 1L.V. Then the photoelectrically converted information according to thelight received from the object to be photographed is further convertedand developed from UJT 11 in the form of digital values, the first-stagethyristor 25 of the pulse counter circuit will be turned on by the firstpulse information, resulting in illumination of the corresponding lamp31 which is connected into the anode circuit of this first-stagethyristor 25. This lamp will become extinguished upon termination of thefirst pulse and the second pulse from UJT 11 will act through thesecondstage thyristor 25 in order to illuminate the second lamp 31, withthe first-stage thyristor being turned off, the second lamp of coursebeing inserted in the anode circuit of the second-stage thyristor 25. Inother words, inasmuch as the gate potential of all thyristors 25 exceptthe first are maintained positive, the first-stage thyristor will beturned on by the first pulse of the information converter, therebylowering the gate voltage of the second-stage thyristor. This permitsthe second pulse to reach the gate of the second-stage thyristor 25 inorder to turn the latter on. At this time the capacitor 26 coupledacross the anodes of the first and second thyristors 25 acts momentarilyas a counter polar voltage source due to the conductivity of thesecond-stage thyristor 25, so that the first-stage thyristor 25 isreversed or inverted in order to be turned off.

In this way, the pulse counter circuit operates in response to thephotoelectrically converted information from the light received from theobject to be photographed to turn on and off the successiveexposureindicating lamps 31 at every increment ocrresponding to l L.V.,so that the successive lamps 31 which are respectively connected withthe successive thyristors are successively turned on during oscillationof the UJ T l 1.

Thus, after the last complete charge-discharge cycle of the outputcapacitor means 7 that lamp 31 will remain illuminated which willindicate the number of cycles or number of light values corresponding tothe analog information initially stored in the input capacitor means 6.On the other hand, the residual analog charge remaining in the balancedcapacitors 6 and 7 is transmitted from the capacitor 7 through thetransistor 32 to the moving coil 33 of the exposure means in order tosituate this coil at an angular position where the arrow will point to agraduation along the curved scale which indicates the magnitude of theresidual analog charge. This scale is relatively large and permits anextremely precise indication of the fractional value remaining after theillumination of the last lamp 31 corresponding to the last light value.Thus it is possible to obtain a reading such as 3.35 L.V., for example,this being the reading shown in FIG. 3 if it is assumed that the thirdlamp remains illuminated after the chargedischarge cycles have beencompleted.

In the event that it is necessary to adjust the bias voltage inconformance with the electrical properties of the input capacitor means6 and the open capacitor means 7, a variable resistor 34 is providedoutput this purpose.

It is to be noted that the information converter of the invention isapplicable not only to shutter controls and exposure meters but also tomany other types of electrical apparatus and instruments, particularlyinstruments and apparatus used for communication purposes. In all suchapplications it is possible, in accordance with the embodiment shown inFIGS. 1 and 3, to incorporate into the information converter anoscillating circuit means which includes UJT 11, thus achieving astabilized operation in a simple way. However, it is to be noted thatuse of UJT 11 is not essential since similar results can be achieved as,for example, by using a bootstrap circuit or a Miller circuit.

With the above-described information converter of the invention thetransistor is inserted into the discharge circuit of the input capacitormeans 6 in order to momentarily open the discharge circuit so as toprevent charging thereof through UJT 11. However, if the error which isincurred during such discharge can be ignored, then the transistor 10 isnot essential and may be replaced with a relay switch or the like so asto prevent possible discharge of the stored information.

Moreover, in the embodiment of FIG. 1 where the information converter ofthe invention is applied to electrical shutter controls, a fineadjustment of bias voltage can advantageously be achieved by a variableresistor such as the bias resistor 23. In addition, if thecharacteristics of transistor 19 are suitably selected, this biasresistor may be omitted.

Additional embodiments of the invention are illustrated in FIGS. 46. Inthe embodiments shown in FIGS. 4-6 the information converter of theinvention includes a marginal operation circuit. In these embodimentsthe input capacitor means for storing the analog information also has anoutput capacitor means inserted in its discharge circuit. Each of theembodiments of FIGS. 4 6 includes at least one Schmitt circuit fortriggering the output in accordance with the predetermined digital-valuecharge to which the output capacitor means is repeatedly charged duringthe chargedischarge cycles, and these embodiments may also includeadditional circuit arrangements such as a circuit for temporarilyopening the discharge circuit during operation of the Schmitt circuitand a discharge oscillation circuit for continuously discharging theoutput capacitor means after the latter has been charged to thepredetermined digital-value charge.

Referring specifically to FIG. 4, there is illustrated therein an inputmeans which includes the photosensitive light-receiving element 41 whichacts as a photoelectric conversion element and which is coupled acrossthe base and collector terminals of the amplifying transistor 43. Thelogarithmic conversion diode 42 which is connected in series withelement 41 is connected across the base and emitter terminals of thetransistor 43. Thus, components 41-43 form a photoelectric conversioncircuit.

The selecting switch 45 corresponds to the switch 8 described above andis electrically connected with the variable resistor 44 in order totransmit the analog information out of the photoelectric conversioncircuit. The input capacitor means 46 is connected to the input meansthrough the switch 45 when the latter is normally closed at its contacta. The output capacitor means 47 is connected into the discharge circuitof the input capacitor means 46 when the switch 45 is displaced to openthe circuit at the contact a and close the circuit at the contact b. Theoutput capacitor means 47 also has a smaller capacitance than the inputcapacitor means 46.

A variable resistor 48 and a switching transistor 49 are connected inseries in the discharge circuit between the capacitors 46 and 47. Theswitching transistor 49 is controlled by a transistor 51 which in turnis controlled by a Schmitt circuit 50. .This Schmitt circuit 50 is madeup of a first-stage transistor 52 and a secondstage transistor 53 whichare electrically connected in a known manner, the base of thefirst-stage transistor 52 being connected to the output terminal A ofthe output capacitor means 47. The transistors 49 and 51 together withthe Schmitt circuit 50 form a circuit for opening the charging circuitof the output capacitor means 47.

The oscillating circuit means of FIG. 4 includes also an additionalSchmitt circuit 54 having a second-stage transistor 55 and a first-stagetransistor 56, the base of a transistor 58 for controlling the switchingtransistor 57 being connected to the collector of the first-stagetransistor 56. The output capacitor means 47 is connected in parallelwith the transistor 57 across the collector and emitter thereof. Thebase of the first-stage transistor 56 of the second Schmitt circuit 54is connected into the output terminal A of the output capacitor means 47thereby permitting a trigger voltage to be applied. Thus, the secondSchmitt circuit 54 and the transistors 57, 58 form that part of theoscillating circuit means which rapidly discharges the output capacitormeans 47 after the latter has been charged up to the digital-valuecharge, while the first Schmitt circuit 50 together with the transistors49 and 51 form that part of the oscillating circuit means forinterrupting the charging of output capacitor means 47 from inputcapacitor means 46 while the output capacitor means 47 is discharged.The circuitry illustrated in FIG. 4 includes also bias resistors 59 and60.

With the embodiment of FIG. 4 the light-receiving component 41 respondsto light and the input means starts operating. While switch 45 is in itsillustrated normal position the analog information is stored as a chargeat the input capacitor means 46. When the switch 45 is displaced so asto engage contact b, the discharge circuit between input capacitor means46 and output capacitor means 47 is closed, and the input capacitormeans 46 will now start to discharge in order to store a charge at theoutput capacitor means 47.

At this time inasmuch as both Schmitt circuits 50 and 51 are in a statewhere the second-stage transistors 53 and 55 are conducting while thefirst-stage transistors 52 and 56 are non-conducting, the switchingtransistor 49 in the discharge circuit will be conductive while theswitching transistor 57 will be non-conductive.

Under these operating conditions the output capacitor means 47 isprogressively charged to an increasing extent. 'When the potential atoutput terminal A has reached the predetermined digital-value charge ofthe output capacitor means 47, both of the Schmitt circuits 50 and54respond so as to switch over in order to place the switchingtransistor 49 in a blocking condition where it is non-conductive whilethe switching transistor 57 now becomes conductive. As a result thecircuit between capacitors 46 and 47 opens while output capacitor means47 discharges. Thus the potential at terminal A drops, and both of theSchmitt circuits 50 and 54 are again restored to their initial state,thereby turnin g transistor 49 on and transistor 57 off. In this way thefirst cycle ends and the second cycle starts. The capacitor means 46will now be further discharged, and the charge-discharge cycles willtake place successively at the capacitor means 47 in this manner.

Thus, the photoelectrically converted input information is furtherconverted into digital information in the form of a series of pulseseach of which has a definite constant level determined by thecapacitance of the output capacitor means 47. When the input capacitormeans 46 has been almost completely discharged, there will be acondition where the charges at both capacitors 46 and 47 are equal. Thislatter residual analog charge is less than the digital-value charge upto which capacitor 47 has been repeatedly charged during the previousoperating cycles, and thus at this time the potential at the outputterminal A is insufficient to form a trigger voltage for the Schmittcircuits 50, 54, so that the potential at output terminal A remainsunchanged This potential which is equal to the residual analog charge isthen taken from the terminal A to be used in the manner described abovein connection with FIG. 1 or in connection with FIG. 3.

The above description refers to an on-off operation of switchingtransistors 49, 57 which takes place in a synchronous manner. Suchoperation, however, may cause the photoelectrically convertedinformation to be discharged directly over the switching transistor 57.Therefore, the on-off operation of switching transistors 49, 57 shouldbe shifted in a predetermined timed relation with respect to each other.With the embodiment of FIG. 4 the first Schmitt circuit 50 is set toswitch over slightly before the second Schmitt circuit 54 while therestoring operation of the first Schmitt circuit 50 is adjusted so thatit is delayed slightly as compared with that of the second Schmittcircuit 54. By setting these Schmitt circuits in this manner theswitching transistor 57 will turn off immediately after thepre-determined digital-value charge has been received by the outputcapacitor means 47 and then the switching transistor 57 will turn onagain. On the other hand, upon termination of the discharge of theoutput capacitor means 47, the switching transistor 57 will first beturned off and then the switching transistor 49 will be turned on.Therefore, the photo-electrically converted information will not besubjected during the discharge operation to any effects which mightresult in any possible errors.

If the residual analog charge stored at the output capacitor means 47 isapplied as a trigger voltage to a timing resistor selecting type ofshutter control system, a continuous adjustment of exposure time may beachieved in the manner described above. In other words with such anelectric shutter control system an exposure time would ordinarily bedetermined only by the selected timing resistor and the timing capacitorwhich has a predetermined capacity, and thus any fractional exposuretime which could not be covered by a selected timing resistor isnecessarily neglected. If the trigger voltage, therefore, is controlledin accordance with the fractional residual analog charge remaining atthe end of the charge-discharge cycles, the adjustment of exposure timewill be made very precisely even at points between the incrementsdetermined by two adjacent timing resistors. The digital information andthe residual analog information achieved with the embodiment of FIG. 4may also be used with an exposure meter as shown in FIG. 3.

The embodiment of FIG. is similar to that of FIG.

4 except that the second Schmitt circuit 54 is eliminated and the firstSchmitt circuit 50 is combined with other structure in order to achievethe desired results. The other features of FIG. 5 are identical withthat of FIG. 4 and the corresponding components are designated by thesame reference characters.

According to FIG. 5, the oscillating circuit means includes only oneSchmitt circuit, namely the Schmitt circuit 50, and a pair of relaymeans respectively formed by relay coils 61 and 62 and by the switches63 and 64 which are respectively controlled by the coils 61 and 62. Therelay coil 61 is inserted in the collector circuit of the second-stagetransistor 53 of Schmitt circuit 50.

The relay coil 61 and the relay switch 63 correspond to and performs thesame operation as the switching transistor 59 of FIG. 4. On the otherhand, the relay coil 62 is inserted into the collector circuit of thefirst-stage transistor 52 of Schmitt circuit 50, and the relay switch 54is connected in parallel with the output capacitor means 47. Relay coil62 and relay switch 64 together replace and correspond to the switchingtransistor 57 of FIG. 4. Since the relay switches 63, 64 are connectedinto the circuit in such a way as to carry out mutually reversedoperations due to the operating characteristics of Schmitt circuit 50,when the output capacitor means 47 is initially charged up to thedigital-value charge, the Schmitt circuit 50 switches over so as to openrelay switch 63 and close relay switch 64. When the potential at outputterminal A drops, the Schmitt circuit 50' will be restored to itsinitial condition, thus closing the relay switch 63 and opening therelay switch 64. In this way the structure of FIG. 5 will also carry outwith the illustrated oscillating circuit means a series ofcharge-discharge cycles at the output capacitor means 47 to achieve theabove results.

The embodiment of FIG. 6 is similar to that of FIG. 5 except that inFIG. 6 a unijunction transistor 65 replaces the relay coil 62 and itsassociated switch 64. All of the rest of the circuitry of FIG. 6corresponds to that of FIG. 5 and the components are designated by thesame reference characters. With the embodiment of FIG, 6 when the outputcapacitor means 47 has been charged up to the predetermineddigital-value charge, the unijunction transistor 65 will be set intooperation so as to assume an oscillating condition, and in this way theseries of charge-discharge cycles will be carried out with thecapacitors finally having the residual analog charge as referred toabove.

Thus, these embodiments of FIGS. 4-6 have the ability of furtherconverting the photoelectrically converted information and any otheranalog information into a series of digital information values eachhaving precisely the same constant level, with a residual analog chargeremaining at the end of the charge-discharge cycles. The oscillatingcircuits of FIGS. 4-6 include the illustrated Schmitt circuits whichoperate as marginal operating circuits in accordance with thedigital-value charge up to which the output capacitor means 47 ischarged during each charge-discharge cycle. These circuits provide areliable and sensitive operation as well as a time lag between theoperations of the components. This permits the discharge oscillationcircuit to carry out an oscillating operation after the dischargecircuit between the capacitors 46 and 47 has been opened for dischargingthe output capacitor means 47 and it then permits the circuit betweenthe capacitor means 46 and 47 to be closed to carry out the nextcharge-discharge cycle. Therefore, the possibility of any undesirabledischarge of input capacitor means 46 during discharge of outputcapacitor means 47 can be totally avoided and the accuracy of operationis improved by proper adjustment of these circuits.

FIGS. 7 and 8 respectively illustrate embodiments of the invention wherethe oscillating circuit means includes at least one monostablemultivibrator. In these embodiments there is also an input capacitormeans for storing the analog information as an analog charge and anoutput capacitor means inserted into the discharge circuit of the inputcapacitor means. The oscillating circuit means has a differentialcircuit for shaping the output from the output capacitor means intopulses as well as a monostable multivibrator circuit triggered by thepulses. This oscillating circuit means will bring about the cyclicalopening and closing of the discharge circuit between the input andoutput capacitor means. Thus, the oscillating circuit means will bringabout momentary opening of the discharge circuit between the input andoutput capacitor means while the output capacitor means discharges afterhaving been initially charged up to the digital-value charge, so thatwith this oscillating circuit means there is also a series ofcharge-discharge cycles for the output capacitor means. If required, an

additional information conversion controlling circuit may be provided tocontrol either the discharge oscillating circuit between the input andoutput capacitor means or the discharge circuit of the output capacitormeans.

Referring now to FIG. 7, the input means includes the photosensitivelight-receiving element 71 which operates as a photoelectric conversionelement and which is connected across the base and collector terminalsof the amplifying transistor 73 to which there is in turn connected thelogarithmic conversion diode 72 which is connected across the base andemitter terminals of the transistor 73. Components 71-73 from thephotoelectric conversion circuit, as referred to above in connectionwith the other embodiments.

This embodiment also has a selecting switch 75 electrically connectedthrough the variable resistor 74 to the photoelectric conversion circuitso as to store the analog information in the input capacitor means 76when the switch 75 is in its normally closed position closing thecircuit through the contact a. Connected in parallel with the inputcapacitor means 76 is the output capacitor means 77 which becomesinserted in the discharge circuit of input capacitor means 76 when theswitch 75 is displaced from contact a and engages contact b. Outputcapacitor means 77 again has a smaller capacitance than the inputcapacitor means 76.

A variable resistor 78 and a normally closed switch 79 are connected inseries in the discharge circuit between the capacitors 76 and 77, thisswitch 79 forming a relay switch controlled by the relay coil 81 whichin turn is controlled by a first monostable multivibrator circuit 80 ofthe oscillating circuit means. This first multivibrator circuit 80consists of a first-stage transistor 82 and a second-stage transistor 83in a well known manner. The collector terminal of the first-stagetransistor 82 is coupled to the series-connected junction betweencapacitor 84 and resistor 85 thus forming a differential circuit topermit trigger pulses to be applied.

A switching transistor 86 is connected to the output terminal A and theoutput capacitor means 77, and the above differential circuit isconnected across the collector and the emitter of the switchingtransistor 86. Relay 81, the first multivibrator 80, the differentialcircuit, and switching transistor 86 together form that part of theoscillating circuit means which opens the discharge circuit of inputcapacitor means 76 when the output capacitor means 77 has been chargedup to the predetermined digital-value charge.

The oscillating circuit means of FIG. 7 further includes a secondmonostable multivibrator circuit 87 made up of a first-stage transistor88 and a secondstage transistor 89. A switching transistor 90 isconnected at its base to the collector of the second-stage transistor89. In the collector circuit of switching transistor 90 there is a relaycoil 91 which controls a normally closed relay switch 92 which isconnected in parallel with the output capacitor means 77. The collectorof the first-stage transistor 88 in the second multivibrator circuit 87is connected to the series-connected junction between capacitor 93 andresistor 94 forming in this way a second differential circuit Thisdifferential circuit is coupled across the emitter and collector of aswitching transistor 95, the base of which is connected to the outputterminal A of the output capacitor means 77. Thus, the secondmultivibrator circuit 87, the switching transistor 90, the relay coil 91and relay switch 92 form that part of the oscillating circuit meanswhich brings about rapid discharge of the output capacitor means 77after the latter has been charged up to the predetermined digital-valuecharge.

With this embodiment, the photoelectric conversion circuit 71-74operates as the input means for feeding to the input capacitor means 76the analog-information charge when the switch is in its normal positionshown in FIG. 7. Upon subsequent opening of the circuit at contact a andclosing of the circuit at contact b, the discharge circuit of capacitormeans 76 is closed and the input capacitor means 76 will now start todischarge, so as to charge the output capacitor means 77 up to thedigital-value charge. Since both of the multivibrators and 81 are on attheir second-stage transistors 83 and 89 and off at their first-stagetransistors 82 and 88, with the entire circuitry operating at this timewith energy derived from the power source such as a battery, the switch79 in the discharge circuit between capacitors 76 and 77 is closed so asto turn switching transistor on and thus maintain switch 92 open.

While the charge at the output capacitor means 77 builds up toward thepredetermined digital-value charge, these conditions remain, and whenthe output capacitor means 77 has been charged to the digitalvaluecharge, the switching transistors 86 and 86 and 95 which are set torespond to this digital-value charge will simultaneously turn on,thereby forming discharge circuits for the capacitors 84 and 93 includedin the two differential circuits. In this way both of the multivibrators80 and 87 will be reversed by way of the trigger pulses derived from thedifferential circuits.

As a result, the second-stage transistor 83 of multivibrator circuit 80will be turned off so as to restore relay 81 to its normal conditionwhere the switch 79 opens thus opening the discharge circuit of theinput capacitor means 76, and this operation takes place simultaneouslywith the turning off of the second-stage transistor 89 in the secondmultivibrator 87. This turns transistor 90 off and restores relay 91 toits normal condition where switch 92 closes so as to short circuit theoutput capacitor means 77. As a result, the discharge circuit of inputcapacitor means 76 is opened while the output capacitor means 77 whichhas been charged up to the digital-value charge is rapidly dischargedthrough the second multivibrator 87. Immediately subsequent to dischargeof the output capacitor means 77 the multivibrators 80 and 87 arerestored to their initial condition thereby opening switch 92 by way ofrelay 91 after discharge of output capacitor means 77 through thetransistor 90 while the latter is in its conductive state. Inasmuch asthe second-stage transistor 83 of the first multivibrator circuit 80 isalso turned on, the switch 79 controlled by relay 81 is closed, and thusthe next charge-discharge cycle will take place. These operations arerepeated bringing about the series of pulses determined by thedigital-value charge up to which the output capacitor means 77 isrepeatedly charged.

After the last of these cycles has been completed there will remain atthe input capacitor means 76 a residual analog charge less than thatrequired to bring the output capacitor means 77 up to the digital-valuecharge, so that the output capacitor means 77 assumes an equal residualanalog charge, and the charge at the output terminal A is insufficientto provide the operating voltage required by the switching transistors86 and 95, and now the potential at output terminal A will remainunchanged. This residual analog charge will then be used in any of theways described above to bring about the control according to the valuebetween successive digital values.

In the above operation the on-off conditions of relay switches 79 and 92are always synchronized. However, with such an arrangement there is adanger that the analog charge at the input capacitor means 76 can discharge directly through the switch 92. Therefore, the timing of theswitches 79 and 92 is shifted to prevent such an operation.

With the embodiment of FIG. 7 the first multivibrator circuit 80 isarranged so that the forward operation thereof is slightly advanced withrespect to the forward operation of the second multivibrator circuit 87,while the return operation of the first multivibrator circuit isslightly delayed with respect to that of the second multivibratorcircuit 87. If the operation-initiating voltage of switching transistor86 is set at a level slightly lower than the switching transistor 95,the reverse operation of the first multivibrator circuit is advanced. Bysetting the first and second multivibrator circuits 80 and 87 in such amanner, the switch 79 will be opened immediately after the outputcapacitor means 77 has been charged to the predetermined digital-valuecharge. This is followed by closing of the switch 92. On the other hand,when the output capacitor means 77 discharges the digital-value chargethe switch 92 will open followed by closing of the switch 79. As aresult the analog charge at the input capacitor means 76 will not besubject to any influence at all during discharge of the output capacitormeans 77, so that any errors which otherwise might occur are avoided.

A continuous adjustment of the exposure time, in the case where thestructure is used in a camera, is achieved in a practical way with thisstructure even with a timing resistor selecting type of electric shuttercontrol by applying the residual analog charge at the output capacitormeans 77 as a trigger control voltage for the electric shutter circuit,as referred to in connection with the embodiment of FIG. 1, for example.In other words with this latter type of electric shutter control,although the exposure time is determined by a selected timing resistorand the timing capacitor which has a constant capacity, any fractionalexposure time corresponding to a value between two adjacent resistorscould not be adjusted without the structure of the invention. Thetrigger voltage, therefore, is controlled in accordance with thefractional value achieved with the residual analog charge, and thus theadjustment of exposure time is made in a highly precise manner at avalue between the increments determined by the timing resistors. Inaddition, the digital and analog information achieved with theinformation converter of the invention as shown in FIG. 7 may be usedwith an exposure meter as shown in FIG. 3.

In the embodiment of FIG. 8 the multivibrator circuit is eliminated andthe multivibrator circuit 87 is modified in such a way as to bring aboutcontrol of the switches 79 and 92 by the multivibrator circuit 87. Allother components are the same as that of FIG. 7 and are designated bythe same reference characters.

With the embodiment of FIG. 8 the relays 81 and 91 are connected inseries. When the second-stage transistor 89 of multivibrator 87 is on,or when the output capacitor means 77 is being charged up to thedigitalvalue charge the switching transistor 90 is on so as to maintainswitch 79 closed, and at this time the switch 92 is opened. As describedabove in connection with FIG. 7 relay 81 includes the normally openswitch 79 while relay 91 includes the normally closed switch 92. Whenthe multivibrator circuit 87 senses that the output capacitor means 77has been charged up to the predetermined digital-value charge, themultivibrator 87 reverses, so that switching transistor 90 becomesnonconductive, thereby bringing about opening of the switch 79 andclosing of the switch 92. When the output capacitor means 77 has beendischarged the multivibrator circuit 87 will return to its initial statethereby opening the switch 92 and closing the switch 79. In this way theembodiment of FIG. 8 also has an oscillating circuit which brings aboutthe charge-discharge cycles at the output capacitor means 77 asdescribed above. Of course, with this embodiment also, after the lastcomplete charge-discharge cycle there will remain at the capacitor 76and 77 the residual analog charge which is used in the manner describedabove.

Thus, with these embodiments the analog information is divided into aseries of digital values all of which are equal, and where the analoginformation is not a precise multiple of the digital value there will bea residual analog information representing a fraction of the digitalvalue. The information conversion controlling circuit controls thedischarge oscillation circuit for discharging the predetermined digitalvalue charge and a circuit is provided for opening and closing thedischarge circuit of the input capacitor means 76, these circuitsforming the oscillating circuit means and having a differential circuitand a monostable multivibrator circuit. In this way it is possible toachieve a reliable and sensitive operation so as to increase theaccuracy. Since it is possible to provide a time lag between that partof the operation when the output capacitor means is discharged and thatpart of the operation when the discharge circuit of the input capacitormeans is opened and closed, the discharge of the output capacitor meanstakes place after the discharge circuit of the input capacitor means hasbeen opened and also the discharge circuit of the input capacitor meansis permitted to close after discharge of the output capacitor means inorder to carry out the next charge-discharge cycle. As a result theinfluence of the input capacitor means will have no effect duringdischarge of the output capacitor means and thus the accuracy of theoperation is maintained.

With the embodiments of FIGS. 7 and 8 the dis charge of the outputcapacitor means 77 with the dropping of the terminal voltage thereof hasno influence on the input means and the closing and opening of thedischarge circuit between the input capacitor means 76 and the outputcapacitor means 77, with the controls being carried out by the operatingconditions of the monostable multivibrator circuitry. Thus, it ispossible after one cycle to again charge the output capacitor meansduring the next cycle after the output capacitor means has beencompletely discharged, thereby providing a precise operation with theoutput capacitor means being precisely charged at each cycle up to thedigitalvalue charge and with a precise residual analog charge remainingafter completion of the series of chargedischarge cycles.

With the embodiments of FIG. 7 and 8, as described above, switch 79 is anormally open switch which closes when the relay 81 is energized.However, by inserting an additional transistor for reversing polarity itis also possible to arrange the relay 79,81 so that the switch 79 is anormally closed switch with the latter becoming open when the relay 81is energized.

FIGS. 9 and 10 respectively illustrate embodiments of the invention foruse in the further conversion of photoelectrically converted analoginformation by way of an information converter according to the presentinvention. In the embodiments of FIGS. 9 and 10 the output capacitormeans C is inserted into the discharge circuit of the input capacitormeans C in which the analog information is stored in the form ofphotoelectrically converted information varying in accordance with amultiple proportion. A second discharge path is newly formed when thefirst discharge path is forced open by the output capacitor means C Thecapacitances of the capacitor means C and C are selected in such a waythat when C and C have a relation such as n C /C a relation such as nl/(2 1) can be satisfied where "y is a 'y-value of a lightreceivingelement contained in the conversion circuit for providing thephotoelectrically converted information. The output capacitor means C isshort-circuited to its associated discharge path when there is atermination of the transfer of the charge between the input and outputcapacitor means C, and C thereby taking out in this way part of theanalog information charged at the input capacitor means C, during atleast one charge-discharge cycle of operation of the output capacitormeans C These discharges of the output capacitor means C of coursedischarge from the latter the digital-value charges up to which theoutput capacitor means C is repeatedly charged during thechargedischarge cycles. Thus, the repeated discharging of the outputcapacitor means C will result in a reduction in the analog informationcharge at the input capacitor means C according to a multiple proportionin contrast with the photoelectrically converted input information whichvaries according to the multiple proportion. Even when the embodimentsof FIGS. 9 and 10 are used with a timing resistor selecting type ofelectric shutter control system, a continuous adjustment of exposuretime may be achieved by controlling the trigger level of the electricshutter controls with the residual analog charge which varies in arelatively narrow range less than a digital-value charge. This narrowconstant range of the digital-value charge may be determined inaccordance with the interval between the successive resistances of thetiming resistors one of which is selected with the electric shuttercontrols.

Referring to FIG. 9, the light-receiving element 101 of this embodimentis connected in series with a bleeder resistor 102, and theseseries-connected components of the input means are in turn connected inseries through a power switch 103 to a power source 104. Thelight-receiving element 101 serves as a photoelectric conversion deviceand the power source 104 may be a suitable battery. This embodiment alsoincludes a change-over switch 105 having the normal position where thecircuit is closed at the contact 105a which is electrically connected tothe junction A between the components 101 and 102. An input capacitormeans C, is connected to the common terminal 1050 of the change-overswitch 105 and through this switch the input capacitor means C isnormally connected in parallel with the bleeder resistor 102.

The normally open terminal b of the change-over switch 105 iselectrically connected to a normally closed terminal 106a of acharge-and-discharge switch 106 which forms the oscillating circuitmeans of this embodiment. The output capacitor means C is a splittingcapacitor connected to the common terminal 1060 of the charge-dischargeswitch 106 so that through the latter switch the splitting capacitor Ccan be situated in the discharge circuit of the input capacitor means Cwhen the switch 105 engages the contact 105b. At this time the switch106 is in its normal position shown in FIG. 9 closing the dischargecircuit between the capacitors C and C through the contact 106a. Thechargedischarge switch 106 has a normally open contact 1061 which can beengaged by the movable switch element to close the discharge circuit ofthe output capacitor means C so as to form in this way a dischargecircuit for the splitting capacitor C FIG. 9 illustrates terminals 107aand 107b for transmitting signals.

Assuming that the switch 103 is closed so that the circuit is energized,then the light-receiving element 101 will receive the light from theobject to be photographed and develops photoelectrically developed information which corresponds to the light which is received. As a resultthe potential at junction A of the bleeder resistor 102 rises in amultiple proportional manner to a level determined by the intensity ofthe light which is received. Therefore, the quantity of informationstored in the input capacitor means C,, which is connected normally inparallel with the bleeder resistor 102, is determined by the potentialat junction A, and in this way the input capacitor means receives theanalog charge. After the input capacitor means C, has been fully chargedin this way, the change-over switch 105 is operated to open the switchat contact 105a and close the switch at contact 105b, thus closing thedischarge circuit of the input capacitor means C,. At this time thecharge-discharge switch 106 is in its normal position shown in FIG. 9,so that charging of the output capacitor means C takes place duringdischarge of the analog charge from the input capacitor means C When thesplitting capacitor C has been charged up to the predetermineddigital-value charge, the charging operation terminates and thus thedischarge of input capacitor means C is interrupted so that thecapacitors C, and C assume a balanced series-connected condition. Atthis time the charge-discharge switch 106 is displaced to move away fromcontact 106a and close the discharge circuit of the splitting capacitorC at the contact 106b, so that in this way a discharge circuit for thesplitting capacitor C is formed and now the splitting or outputcapacitor means C, will discharge. Upon return of the switch 106 to itsnormal position, the splitting capacitor will again be charged with theanalog charge from the input capacitor means C in the manner describedabove, thus bringing about a second operating cycle with a new balancedstate of capacitors C and C resulting after the next charging of theoutput capacitor means C up to the digital-value charge. Now thecharge-discharge switch 106 will be switched over to complete thedischarge circuit of the splitting capacitor C and in this way thecircuitry will operate to bring about the charge-discharge cycles of theoutput capacitor means C These repeated cycles will reduce in a stepwisemanner the analog charge at the input capacitor means C so that thedigital values determined by the balanced condition of the capacitors Cand C will result in intermittent reduction of the analog charge at theinput capacitor means C and these digital-value charges will appearacross the output terminals 107a and l07b. Since the resulting digitalinformation has been achieved under conditions determined by thecapacitances of the input capacitor means C, and the splitting capacitorC they do not necessarily vary in accordance with a multiple proportionin contrast to the photoelectrically converted input information whichvaries in accordance with a multiple proportion. The lightreceivingelement 101, the input capacitor means C and the output or splittingcapacitor means C:

I therefore are constructed so as to have a certain interrelationship soas to thereby impart to the resulting digital information acharacteristic corresponding to the photoelectrically converted inputinformation which v This equation may be transformed according to theLaplaces transformation, to give 1 1 saw.

20 Thus, whenr 4 or when C, and Cg are balanced, the terminal voltage V,of the splitting condenser C: will be V (s) [(s) l/SC 2 2( l 1/( 1+ 2)l'1 (In the above equations, the sign represents that V and V, are inoppositeporality with each other.) Assume that C nC n C /C equation (1)will be transformed as V nC (nC C V n/(n l) V,

Furthermore, if n/(n l) is to be expressed by m, equation (1) will betransformed as V m.V,

More concretely, if the condensers C and C have an equal capacity, mwill duly be unity. Thus On the other hand, ifC C and n= 1, 2, 3, 4,. k,in will be l, 4/5, k/(k+ 1).

Since m can be regarded as a common ratio of a geometrical proportiondecreasinggprogressively, m will be called a reduction ratio in thisdescription. The reduction ratio. means that the balanced voltage V of Cand C will necessarily be smaller as compared with V Now a photoelectricconversion circuit consisting of a light-receiving element 101 and ableeder resistor 102 will be described. As is known, the potential atthe connecting terminal A in FIG. 9, or the terminal voltage V R of thebleeder resistor 102 will be expressed as where R light-correspondingresistance of the lightreceiving element 101, r resistance of thebleeder resistor 102, E power voltage In the region where V and R are ina linear relationship with each other, there will be a relation as R r,thus If the resistance of the light-receiving element 101, when itreceives no light, is to be expressed by R,

where b a value corresponding to a specific L.V. 'y 3 -value of thelight-receiving element 101 Therefore This is a geometric proportionvarying as 2 2"" 2 The common ratio p of the geometric proportion isFrom equation (5) it is apparent that if 'y is so selected that 'y l,the value of n will be n 1. Therefore, two capacitors having equalcapacitance can be used as the input capacitor means C and the splittingor output capacitor means C Generally when a y-value is given, therelationship between C; and C will be duly determined. This isconvenient because C, and C need not be so selected that they have aninteger ratio therebetween. It is only seldom that one encoun ters inpractice the case where 'y-values commonly used in production areintegers. Moreover, in view of the fact that the smaller 'y-value iscapable of covering a wide range of light, it is preferred to select alightreceiving element having a smaller 'y-value. As described byselecting 'y and n which have a relation such as n 1/( 2 1), it will bepossible to impart a multiple proportion characteristic as shown by thephotoelectrically converted input information to the digital informationtaken out at the output terminals 107a, 107b. In other words, thephotoelectrically converted input information are multipleproportionally increasing analog values, while the further convertedoutput information are multiple proportionally decreasing digitalvalues.

FIG. 10 shows an embodiment where the information converter of theinvention is applied to a timing resistor selecting type of electricshutter control system in order to provide a continuous adjustment ofthe exposure time. The information converter shown in FIG. 10 is thesame as that of FIG. 9 and the corresponding components are designatedby the same reference characters. An FET (field effect transistor) 108is connected at its drain in series with an indicating lamp and anelectromagnetic relay 1 10. As is known, FET 108 is a high inputimpedance transistor having a leakage current which for practicalpurposes can be ignored. The starting voltage of FET 108 is set inaccordance with the resistance interval defined by the timing resistorswhich are used to determine the exposure value of the shutter controls.For example if the timing resistors are arranged at intervalscorresponding to 1 L.V., the starting voltage of PET 108 should be setto 1 L.V. so that FET 108 starts operation when the input capacitormeans C, has been charged toa potential corresponding to l L.V. Thus,the indicating lamp 109 and electromagnetic relay 110 will be keptoperating until the operating voltage drops below the starting voltage.A switch 110a which operates in response to the electromagnetic relay110 is arranged in such a way that it serves as a power-supplying switchfor a known astable multivibrator circuit 111 which forms with theswitch 106 part of the oscillating circuit means of FIG. 10. Atransistor 112 is coupled in such a way that it turns on in response tooscillating information from the multivibrator circuit 111. Thecollector of transistor 112 is connected in series with a secondelectromagnetic relay 113 and its associated switch 114. Theelectromagnetic relay 113 is provided for automatically operating thecharge-discharge switch 106.

A second light-receiving element is arranged in the electric shuttercontrol circuit in such a way that the photoelectrically convertedinformation produced thereby is applied to a selection signal circuit116 which transmits a signal for selecting a given timing resistor inthe timing resistor selection circuit 117 which consists of a set oftiming resistors. The timing resistor which is selected forms a delaycircuit together with the timing capacitor 118. In response to the timeconstant determined by the delay circuit a switching transistor 119 isturned on so as to control the electromagnet 120 which determines whenthe exposure will be terminated. A shutter release switch 121 operatesin synchronism with actuation of the shutter-tripping button to beclosed for starting the exposure. A trigger control circuit is formed byway of a transistor 122 which is connected at its emitter to a triggerresistor 123 and at its base, together with the gate of PET 108, to thepositive terminal of the input capacitor means C; so as to control inthis way transistor 122 with the residual analog charge across the inputcapacitor means C for varying the trigger voltage.

When the power source switch 103 is closed in the initial stage of theshutter-releasing operation, the input capacitor means C will storetherein the multiple proportionally varying photoelectrically convertedinformation resulting in illumination of indication lamp 109 andoperation of the electromagnetic relay 110. As a result the switch a isclosed and the multivibrator circuit 111 will start oscillating. Uponchange-over of the switch 105 from closing the input to the capacitormeans C by way of the contact 105a to closing the discharge circuit ofcapacitor means C by way of the contact 10517, as well as by closing ofthe switch 114, transistor 112 is placed in a continuous on-and-offoperation. The charge-discharge switch 106 will accordingly make achange-over operation alternately between the normal closed terminal106a and the normally open terminal 106b. Therefore, the analog chargein the input capacitor means C will be reduced through increments, asdescribed in connection with FIG. 9, or in other words the storedinformation will be reduced according to a multiple proportion. When theinformation stored as an analog charge at the input capacitor means Cdecreases in this manner to a value corresponding to 1 L.V., FET 108becomes inoperative, so that the indicating lamp 109 becomesunenergized, and electromagnetic relay 110 is restored to its initialcondition. Therefore, the multivibrator 111 stops operating, thetransistor 112 and the electromagnetic relay 113 are restored to theirinitial condition, while the charge-discharge switch 106 assumes itsnormal position engaging contact 106a. Inasmuch as input capacitor meansC, and the splitting or output capacitor means C are balanced in thiscondition, the input capacitor means will not discharge and the terminalvoltage across the input capacitor means C will remain unchanged.

On the other hand, inasmuch as the residual analog charge remaining atthe input capacitor means C, is applied as a base voltage to thetransistor 122, the conditions which will determine the adjustment ofthe exposure time will be determined upon closing the shutterreleaseswitch 121, by way of the trigger-control voltage developed by thetransistor 122 as well as by the time constant which in turn isdetermined by the selected timing resistor of the circuit 117 and thetiming capacitor 118. In other words a fractional part of the lightreceived from the object to be photographed, or a portion of this lightwhich cannot be covered by a selected timing resistor is covered by thetrigger voltage controlled by the information converted with theinformation converter of the invention, thereby achieving a continuousadjustment of exposure time consistently with the light received fromthe object to be photographed.

As has been proved above, as long as the condition n l/(2 l) issatisfied, input capacitor means C and the splitting capacitor C storetherein an equal quantity of information in their balanced condition.Assuming now that the starting voltage of PET 108 is 0.1V and thepotential of the photoelectrically converted information is 3.2V, thebalanced voltage between the capacitors C, and C will drop in incrementsas follows:

When the balanced voltage is 0.1V, FET 108 will be operating. Thus, theindicating lamp 109 and electromagnetic relay 110 will still beoperating. When the charge-discharge switch 106 makes the next switchingoperation, the balanced voltage will drop to 0.05V to thereby render FET108 inoperative. Now indicating lamp 109 will be turned off,electromagnetic relay 110 will be restored to its initial condition, andthe balanced voltage 0.05V will be applied to the trigger circuit of theelectric shutter controls.

In the same way, if the potential of the photoelectrically converted is0.7V, the resulting balanced voltage will be as follows:

0.7V, 0.35V, 0.175V, 0.0875V Thus, the ultimate balanced voltage will be0.0875V, and this is the residual analog charge which will be applied tothe trigger circuit as a control voltage therefor. In this embodimentthe charge-discharge switch 106 is arranged in such a way as to beautomatically switched over by means of the multivibrator circuit 111,but the above-referred to residual analog voltage may also be obtainedby a manual operation of the chargedischarge switch 106 if FET 108 andindicating lamp 109 are arranged in the manner indicated by the dotdashlines in FIG. 9. In this case extinguishing of the indication lamp 109indicates that the trigger voltage has been reached.

As is apparent from the above description when with the embodiment ofFIGS. 9 and 10 the light-receiving element and capacitors C and C areset in such a way that there exists the relationship n 1/(2 1), it iscapable of converting the photoelectrically converted and multipleproportionally varying input analog infor mation into digital outputinformation which reduce accordingly the multiple proportion. Thus acontinuous adjustment of exposure time can be made with a timingresistor selecting type of electrical shutter device by selecting givendigital information as a reference information corresponding to thelighting condition which in turn corresponds to an interval between thetiming resistors and by controlling the trigger circuit with theresidual analog charge which is less than the reference value. As isclearly understood from the relation n l/(2 l), the light-receivingelement may be used in a lower region of y-value. This permits providingan electrical shutter control with an excellent response characteristicover a wide range of light intensity. In addition, the lack ofuniformity of y-value provided by the light-receiving element asavailable on the market can be compensated by selecting capacitorshaving suitable capacitances.

The information converters according to the present invention may bealso constructed for manual operation. This is advantageous in order tosimplify the construction of the information converter. In addition theinformation converters of the embodiments of the present invention areof practical value when applied to electric exposure meters.

In summary, the present invention provides information converters whichhave the ability to convert photoelectrically converted information oflight received from the object to be photographed or other analoginformation into continuous digital output information in the form of aseries of pulses all having equal constant levels and in the form of anultimate output residual analog charge, with the period of the digitalinformation being optionally adjusted by means, for example, of avariable resistor. Furthermore, the present invention may beadvantageously applied to a timing resistor selecting type of electricshutter control as a trigger voltage control means. More specifically,since the trigger voltage of this type of electic shutter control can becontrolled by the residual analog charge, which can be obtained byfurther converting the electrically converted information of lightreceived from the object to be photographed, the unsatisfactory step orincrement type of adjustment of exposure time by a selected timingresistor and the timing capacitor can be supplemented to achieve acontinuous adjustment of exposure time. The information converter of theinvention may be made as a separate device which is independent of theelectric shutter control device.

Furthermore, when the information converter according to the inventionis applied to an electric exposure meter, the exposure value can beindicated at equal intervals by means of the digital output from theinformation converter while the fractional fine indication of exposurevalue can be obtained by means of the residual analog charge developedby the information converter. In this case the fractional fineindication can be made by use of the needle connected to the moving coilto achieve an enlarged indication of the fine, fractional analog charge.I

It is to be noted, however, that the present invention is not limited toapplication to electric shutter devices and electric exposure meters andis also applicable to any communication apparatus and many otherdevices.

What is claimed is:

1. In an information converter, input capacitor means for storing ananalog-information charge, input means electrically connected with saidinput capacitor means for charging the latter to an extent determined bythe analog information, output capacitor means having a capacitance lessthan said input capacitor means, oscillating circuit means electricallyconnected with both of said capacitor means for carrying out a number ofcharge discharge cycles during which said output capacitor means ischarged from the analog-information charge stored by said inputcapacitor means up to a predetermined digital-value charge, thendischarged, then again charged from said input capacitor means up tosaid digital-value charge, and so on until, in the event that saidanalog-information charge is not a precise multiple of saiddigital-value charge, both of said capacitor means assume a balancedcondition where they respectively have equal residual analog chargeseach of which is less than said digital-value charge, and detectingmeans electrically connected with at least one of said capacitor meansfor detecting said residual analog charge, so that a value correspondingto the number of digital-value charges plus said residual analog chargewill correspond precisely to said analog information.

2. The combination of claim 1 and wherein said input means iselectrically connected with said input capacitor means for charging thelatter with an analoginformation charge corresponding to the light at anobject which is to be photographed.

3. The combination of claim 2 and wherein a shuttercontrol means of acamera is electrically connected with said detecting means to betriggered at least in part in accordance with said residual analogcharge for determining film exposure.

4. The combination of claim 3 and wherein a photosensitive means iselectricaly connected with said shutter-control means for controllingthe latter in a stepwise manner according to the number of times saidoutput capacitor means is charged up to said digital-value charge.

5. The combination of claim 2 and wherein said detecting means is amoving coil means of a light meter for indicating said residual analogcharge as a fractional light value, said light meter having anindicating means operatively connected with said oscillating circuitmeans for indicating a light value corresponding to the number ofcharge-discharge cycles carried out by said oscillating circuit means.

6. The combination of claim 1 and wherein said oscillating circuit meansincludes unijunction transistor.

7. The combination of claim 1 and wherein said oscillating circuit meansincludes at least one Schmitt circuit.

8. The combination of claim 7 and wherein said oscillating circuit meansincludes a pair of Schmitt circuits.

9. The combination of claim 7 and wherein said oscillating circuit meansincludes a single Schmitt circuit and a pair of relay means electricallyconnected therewith and with said input and output capacitor means forproviding said charge-discharge cycles.

10. The combination of claim 7 and wherein said oscillating circuitmeans includes a single Schmitt circuit and a relay means andunijunction transistor means electrically connected therewith and withsaid input and output capacitor means for carrying out saidcharge-discharge cycles.

11. The combination of claim 1 and wherein said oscillating circuitmeans includes at least one monostable multivibrator circuit means.

12. The combination of claim 10 and wherein said oscillating circuitmeans includes a pair of monostable multivibrator circuit means.

13. The combination of claim 11 and wherein said oscillating circuitmeans includes a single monostable multivibrator circuit means and apair of relay means controlled thereby and operatively connected withsaid input and output capacitor means for carrying out saidcharge-discharge cycles.

14. The combination of claim 1 and wherein said oscillating circuitmeans includes a charge-discharge switch means having a chargingposition connecting said input capacitor means to said output capacitormeans for charging the latter up to said digital-value charge duringeach of said cycles and a discharge position for disconnecting saidoutput capacitor means from said input capacitor means and fordischarging said output capacitor means during each of said cycles.

15. The combination of claim 14 and wherein said oscillating circuitmeans includes an astable multivibrator means operatively connected withsaid chargedischarge switch means for automatically moving the latterbetween said positions thereof.

1. In an information converter, input capacitor means for storing ananalog-information charge, input means electrically connected with saidinput capacitor means for charging the latter to an extent determined bythe analog information, output capacitor means having a capacitance lessthan said input capacitor means, oscillating circuit means electricallyconnected with both of said capacitor means for carrying out a number ofcharge-discharge cycles during which said output capacitor means ischarged from the analog-information charge stored by said inputcapacitor means up to a predetermined digital-value charge, thendischarged, then again charged from said input capacitor means up tosaid digital-value charge, and so on until, in the event that saidanalog-information charge is not a precise multiple of saiddigital-value charge, both of said capacitor means assume a balancedcondition where they respectively have equal residual analog chargeseach of which is less than said digital-value charge, and detectingmeans electrically connected with at least one of said capacitor meansfor detecting said residual analog charge, so that a vaLue correspondingto the number of digital-value charges plus said residual analog chargewill correspond precisely to said analog information.
 2. The combinationof claim 1 and wherein said input means is electrically connected withsaid input capacitor means for charging the latter with ananalog-information charge corresponding to the light at an object whichis to be photographed.
 3. The combination of claim 2 and wherein ashutter-control means of a camera is electrically connected with saiddetecting means to be triggered at least in part in accordance with saidresidual analog charge for determining film exposure.
 4. The combinationof claim 3 and wherein a photosensitive means is electrically connectedwith said shutter-control means for controlling the latter in a stepwisemanner according to the number of times said output capacitor means ischarged up to said digital-value charge.
 5. The combination of claim 2and wherein said detecting means is a moving coil means of a light meterfor indicating said residual analog charge as a fractional light value,said light meter having an indicating means operatively connected withsaid oscillating circuit means for indicating a light valuecorresponding to the number of charge-discharge cycles carried out bysaid oscillating circuit means.
 6. The combination of claim 1 andwherein said oscillating circuit means includes unijunction transistor.7. The combination of claim 1 and wherein said oscillating circuit meansincludes at least one Schmitt circuit.
 8. The combination of claim 7 andwherein said oscillating circuit means includes a pair of Schmittcircuits.
 9. The combination of claim 7 and wherein said oscillatingcircuit means includes a single Schmitt circuit and a pair of relaymeans electrically connected therewith and with said input and outputcapacitor means for providing said charge-discharge cycles.
 10. Thecombination of claim 7 and wherein said oscillating circuit meansincludes a single Schmitt circuit and a relay means and unijunctiontransistor means electrically connected therewith and with said inputand output capacitor means for carrying out said charge-dischargecycles.
 11. The combination of claim 1 and wherein said oscillatingcircuit means includes at least one monostable multivibrator circuitmeans.
 12. The combination of claim 10 and wherein said oscillatingcircuit means includes a pair of monostable multivibrator circuit means.13. The combination of claim 11 and wherein said oscillating circuitmeans includes a single monostable multivibrator circuit means and apair of relay means controlled thereby and operatively connected withsaid input and output capacitor means for carrying out saidcharge-discharge cycles.
 14. The combination of claim 1 and wherein saidoscillating circuit means includes a charge-discharge switch meanshaving a charging position connecting said input capacitor means to saidoutput capacitor means for charging the latter up to said digital-valuecharge during each of said cycles and a discharge position fordisconnecting said output capacitor means from said input capacitormeans and for discharging said output capacitor means during each ofsaid cycles.
 15. The combination of claim 14 and wherein saidoscillating circuit means includes an astable multivibrator meansoperatively connected with said charge-discharge switch means forautomatically moving the latter between said positions thereof.